You may have seen recent headlines that heralded studies indicating that diet soda consumption was related to weight gain. A USA Today headline from a July 10, 2013 article read, “Study: Diet soda doesn’t help you lose weight” (Diet Soda Article). Another on the Reader’s Digest web site asks, “Is Diet Soda Making You Fat?” (Reader’s Digest Article). Furthermore, WebMD reports that searching “diet soda” and “weight” using a popular browser found that 49 of the top 50 hits were for stories that warned readers of the link between diet soda and weight gain (WebMD Article). Why has this issue been in the news in recent months? It turns out that a few scientific studies were published over the past several months, purporting this idea that diet soda consumption may actually lead to weight gain, rather than what most people would expect, weigh loss. Let’s have a closer look at those studies and also consider this issue in light of a larger body of scientific research on this topic.
It turns that the recent attention to this issue results from studies with laboratory rats and from observational studies in humans. In the rat studies, published by Drs. Swithers and Davidson at Purdue University (Swithers S and Davidson T – PubMed – NCBI), the researchers noted an association between non-nutritive sweetner consumption (e.g. saccharin) and weight gain. The researchers suggested that rats consuming saccharin, as opposed to rats ingesting table sugar, took in more calories and gained more weigh over time. But, will this finding hold true in humans?
Other recent epidemiological studies, consisting of large numbers of people, reported that those who drank more diet sodas gained more weight over time. One study tracked more than 5000 adults in the San Antonio Heart Study. The second (the Framingham analysis) reported an association between intake of both sugar-sweetened sodas and diet sodas and development of metabolic syndrome, which is cluster of symptoms linked to obesity. However, since both of these studies were observational, it is not possible to say with certainty whether consumption of diet sodas has a direct effect on body weight.
These studies were rapidly popularized by the media and online bloggers, and soon this message was out for all to see. Interestingly, not everyone agrees with these findings and many past studies have not identified such an association. A recent review of past studies on this topic, published in the American Journal of Nutrition (AJCN Article), came to different conclusions, namely that the purported mechanisms by which non-nutritive sweetners promote energy intake and contribute to weight gain are not supported by the current available evidence. The authors do however recommend that this possibility should be further considered in long-term, randomized controlled clinical trials.
The jury is thus still out on this issue, despite all the recent negative press regarding consumption of artificial sweetners. Importantly two respected scientific organizations support the use of no calorie sweetners to restrict calorie and sugar intake (the American diabetes Association and the American Dietetic Association). This thus leaves us as individuals with a sort of dilemma. Should we restrict intake of artificial sweetners? Which studies are correct? The best advice may be to consume these food additives in moderation and await more definitive research which will undoubtedly be undertaken very soon.